Embodiments of the invention relate generally to a photovoltaic (PV) system, and more particularly to improved systems and methods for mounting a microinverter to a PV panel and forming an electrical connection therebetween.
PV systems include PV modules arranged in arrays that generate direct current (DC) power, with the level of DC current being dependent on solar irradiation and the level of DC voltage dependent on temperature. PV systems may be constructed either as an inverter system or a microinverter system. A typical inverter system uses DC wiring to electrically couple multiple PV panels to a single inverter. The inverter then converts the DC energy from the PV panels into AC energy, such as AC energy suitable for transfer to a power grid. A typical microinverter system, on the other hand, uses DC wiring and a junction box to electrically connect a microinverter to each PV panel, forming an AC PV module 10 as shown in FIG. 1. In this AC PV module system, each microinverter assembly 12 converts the DC energy from its respective panel into AC energy suitable for transfer to a power grid. The junction box 14 of each PV module 10 contains bypass diodes that allow each AC PV module 10 to maintain peak efficiency under partial shading conditions by bypassing sections of cells in the AC PV module 10 which are not receiving solar irradiation. By removing AC PV module cells that are not producing DC power from the electrical connection, the PV system ensures that these non-producing AC PV module cells do not draw DC power from the PV system, which may reduce power to the load and cause AC PV module overheating.
The construction of typical AC PV modules makes infield repairs time consuming. In the case of an internal wiring issue, a technician must diagnose the fault onsite in order to determine what component of the module to repair. An electrical fault may occur within the microinverter assembly 12 itself, which is secured to a PV panel 16, the diodes within junction box 14, or between the two (2) DC connections 18, 20 that contain respective DC connectors 22, 24 that connect the junction box 14 and the microinverter 26. Since a unique key or tool must be used to remove each of the junction box 14 and the microinverter 26, and to dissemble the DC connectors 22, 24 to determine which component of the AC PV module 10 is faulty, the onsite repair is time consuming and costly. Further, the wired connection between the PV panel 16 and the microinverter 26 typically includes approximately one to two feet of DC cable and a junction box, which adds cost to the PV system.
To meet the national electrical code (NEC), special DC wiring and grounding specifications exist for DC module strings capable of producing voltages as high as 600 volts. Further, installers must properly manage the safety risks posed by the potentially lethal DC voltages when dealing with installation of DC wiring. As a result, a certified electrical is used for proper installation of the special DC wiring. Because all of the wiring is done on-site, the process for installing the DC wiring of the PV system accounts for a significant amount of the time and cost of the overall installation of the PV system.
Therefore, it would be desirable to provide a PV system with DC connections that are easily field repairable, have a reliable and stable connection, and are less costly than the DC connections of known PV systems.